Vision systems frequently entail detecting and tracking a subject's eyes in an image generated by a video camera. In the motor vehicle environment, for example, a camera can be used to generate an image of the driver's face, and portions of the image corresponding to the driver's eyes can be analyzed to assess drive gaze or drowsiness. See, for example, the U.S. Pat. Nos. 5,795,306; 5,878,156; 5,926,251; 6,097,295; 6,130,617; 6,243,015; 6,304,187; and 6,571,002, incorporated herein by reference.
Since a high percentage of people wear some form of eyeglasses when driving, a vehicular vision system must be capable of reliably monitoring the driver's eyes regardless of whether the driver is wearing eyeglasses. And yet eyeglasses complicate eye monitoring because they can significantly change the appearance of the driver. Moreover, eyeglass lenses and frames can obscure the vision system's view of the driver's eyes, and produce glare spots due to reflected ambient and active illumination. While there are special lighting and image processing techniques for addressing the challenges posed by eyeglasses, using these techniques for all drivers would impose an unnecessary burden on the vision processor. Accordingly, what is needed is a simple but reliable way of detecting whether the driver is wearing eyeglasses so that the vision system can be configured accordingly.